The present invention relates to a method for connecting conductive members, such as connecting FPCs (flexible printed circuit) each other, or connecting the FPC to a terminal.
In FIG. 11 of the attached drawings, the FPC 1 is formed by arranging a circuit pattern (conducting portion 3) being a conductor such as copper on an insulating film 2 as polyimide through an adhesive material, and further pasting thereon the same insulating film 4 as the above mentioned film through the adhesive material. Since such an FPC 1 has flexibility and a conducting portion 3 is patterned between the insulating films 2 and 4, wiring is very easy, and in particular, the FPC is much adopted to connections between complicated circuits or units.
Incidentally, for connecting the FPCs 1 each other, as shown in FIGS. 12 or 13, it is generally practiced to employ a connecting method using a supersonic welding technique or a spot welding technique.
In FIG. 12, the connecting method using the supersonic welding technique comprises arranging the mutual FPCs 1 by piling them in vertical directions, holding their vertical both sides between a supersonic welding horn 5 and an anvil 6, and applying supersonic vibration thereto so as to weld conducting portions 3 each other (as to a connected condition, refer to FIG. 14).
In FIG. 13, the connecting method using the spot welding technique comprises arranging the mutual FPCs 1 having parts removing insulating films 2 and 4 by meeting parts 7 without the insulating films 2 and 4 to pile them in the vertical directions, holding both vertical ends between electrodes 8, concentrating electric current and pressure for locally heating them so as to weld the conducting portions each other (resistance welding) (as to a connected condition, refer to FIG. 14).
The above mentioned related methods have the following problems.
Firstly, the connecting method using the supersonic welding technique is involved with a problem that a connection accomplished state cannot be confirmed from the outside. Unless confirming from the outside, occurrence of non-welded parts as shown with an arrow P in FIG. 15 cannot be found (only the insulating films 2 and 4 are welded, and the mutual FPCs 1 are thereby fixed each other). Further, another problem is that in the connecting method using the supersonic welding technique, if frictional heat by the supersonic vibration is large, a conducting portion 3 is ruptured.
Secondly, the connecting method using the spot welding technique has a problem that because current is applied between electrodes 8, the insulating films 2 and 4 must be in advance removed from both upper and rear faces for forming the parts 7 removing the insulating films 2 and 4, taking very much trouble.
As to other problems, being in common to the respective connecting techniques, the insulating films 2 and 4 are deformed owing to connecting heat, spoiling insulation. In addition, when connecting, pressure must be effected from vertical direction by connecting units, inviting rupture of the conducting portion 3 or large sizing scales of units. After connecting (after welding), since exposed parts occur in the conducting portion 3 in vertical direction, both sides must be sealed with insulators 9, also herein taking very much trouble.
It is therefore an object of the present invention to provide a method for connecting FPCs capable of heightening workability, avoiding ruptures in the conducting portions and reduction of insulation, and enabling to confirm the connection accomplished state from the outside, thereby to increase reliability.
In order to achieve the above object, according to the present invention, there is provided a method for connecting conductive members comprising the steps of:
providing a first conductive member;
providing a second conductive member; and
jetting droplets of molten metal so as to form a connecting portion which electrically connects the first conductive member with the second conductive member.
Preferably, the method further comprising the steps of:
solidifying the connecting portion provided between the first conductive member and the second conductive member: and
sealing the connecting portion and an exposed portion of the first and second conductive members with an insulator.
Preferably, the first conductive member and the second conductive member are contacted with each other.
Preferably, the first conductive member and the second conductive member are separated from each other.
Preferably, the first conductive member and the second conductive member are piled each other in a vertical direction.
Here, it is preferable that an insulating film is interposed between the first conductive member and the second conductive member.
In the method, the conductive members are easily electrically connected by the connecting portion comprised of the molten metal drops, and after connection, whether the connection is accomplished or immature is seen through visual confirmation of an adhered condition of jetted or dripped the molten metal drops. Further, heat toward the conductive members at connecting is low in parts under connection because of using molten metal drops, and molten metal drops never make heat causing rupture of the conductive member or reduction of insularity of insulating film when the conductive member is a conductive portion of a flexible printed circuit. Besides, a part exposed in the conductive member is limited as small as possible, and sealing of an insulator after connection is enough only at the exposed portion of the conductive member, thereby to increase workability.
Preferably, at least one of the first conductive member and the second conductive member has a through-hole in which the connecting portion electrically connects the first conductive member with the second conductive member via the through-hole.
In the method, the conductive members are easily electrically connected by the connecting portion comprised of the molten metal drops, and after connection, whether the connection is accomplished or immature is seen through visual confirmation of an adhered condition of jetted or dripped the molten metal drops. Further, heat toward the conductive members at connecting is low in parts under connection because of using molten metal drops, and molten metal drops never make heat causing rupture of the conductive member or reduction of insularity of insulating film when the conductive member is a conductive portion of a flexible printed circuit. Besides, a part exposed in the conductive member is limited as small as possible, and sealing of an insulator after connection is enough only at the exposed portion of the conductive member, thereby to increase workability.
Preferably, a flexible printed circuit is constituted of a conductive portion covered with an insulating film. The first conductive member and the second conductive member are exposed conductive portions, each of the exposed conductive portions which formed by removing the insulating film from the flexible printed circuit so as to expose the conductive portion.
Preferably, a flexible printed circuit is constituted of a conductive portion covered with an insulating film. One of the first conductive member and the second conductive member is an exposed conductive portion which formed by removing the insulating film from the flexible printed circuit so as to expose the conductive portion, and another is a terminal.
In the methods, since the conductive member is the flexible printing circuit or the terminal, the connection is available in the flexible printing circuit to the flexible printing circuit or the flexible printing circuit to the terminal.